Use of monohydrate zinc acetylacetonate as halogenated polymer stabilizer and preparation method

ABSTRACT

The subject of the present invention is the use of zinc ateylacetonate comprising at least 4.4% by weight of water as halogenated polymer stabilizer.Its subject is likewise a process for the preparation of zinc acetylacetonate monohydrate, in which a zinc oxide and/or hydroxide and acetylacetone are brought into contact, in the presence of a solvent; the said solvent being used with a quantity of between 20 and 200 parts by weight, per 100 parts by weight of acetylacetone.

The subject of the present invention is the use of zinc acetylacetonate,predominantly crystallized in the form of a monohydrate compound, asstabilizing agent for halogenated polymers.

Its subject is likewise a process for the preparation of the said zincacetylacetonate.

Anhydrous zinc acetylacetonate is a product known in the literature, aswell as its role of stabilizing halogenated polymers, and mostparticularly chlorinated polymers, such as poly(vinyl chloride).

However, while the importance of this compound is not under challenge,it exhibits, nevertheless, the disadvantage of having to be stored underspecial conditions, free of water. In the opposite case, under theeffect of ambient humidity, the product cakes and can no longer be usedas it is.

The aim of the present invention is to provide another type of zincacetylacetonate which can be used as agent stabilizing halogenatedpolymers, not exhibiting the above disadvantage.

The first subject of the present invention is therefore the use of zincacetylacetonate comprising at east 4.4% by weight of water, ashalogenated polymer stabilizer.

It should be noted that for the sake of simplicity and of clarity of thedisclosure which follows, the zinc acetylacetonate whose use constitutesone of the subjects of the invention, will be described as“monohydrate”, to distinguish it from the “anhydrous” zincacetylacetonette used up until now.

Likewise its subject is a process for the preparation of zincacetylacetonate monohydrate, in which a zinc oxide and/or hydroxide andacetylacetone are brought into contact, in the presence of a solvent;the said solvent being used with a quantity of between 20 and 200 partsby weight, per 100 parts by weight of acetylacetone.

It is important to specify that up until now, reference has only beenmade to zinc acetylacetonate in anhydrous form, as halogenated polymerstabilizer. It is indeed known in this field that the presence of waterin these compositions should be as low as possible. Indeed, given thehigh temperatures for forming such formulations, the water is vaporizedand, upon escaping, can cause the appearance of defects in the finalarticle, which is obviously not desirable.

However, it has been found that zinc acetylacetonate monohydrate,contrary to what was expected, did not exhibit any disadvantage when itwas introduced into a halogenated polymer formulation. Indeed, duringthe use of the composition thus additivated, the appearance of bubblesor other defects due to the evacuation of the water is not observed.

Furthermore, in the publication by E. Lippert and M. R. Truter, whichappeared in Journal of Chemical Society, 1960, p. 4996-5006, it isindicated that the monohydrated form of zinc acetylacetonate is the moststable crystalline form. Persons skilled in the art would therefore haveexpected to have a lower stabilizing activity than the anhydrouscompound. However, here again, nothing of the such was observed.

It should be noted finally that the monohydrate compound is stable overtime and does not cake, even when it is stored under an ambientatmosphere, that is to say with some humidity.

However, other characteristics and advantages of the present inventionwill appear more clearly on reading the description which follows.

The composition used in the invention is therefore zinc acetylacetonatecomprising at least 4.4% by weight of water.

More particularly, the water content is between 4.4 and 8.8% by weight.According to a particular variant of the invention, the composition usedhas a water content of between 4.75% and 8.15% by weight. According toan advantageous variant of the invention, the compound has a structuresimilar to that of zinc acetylacetonate monohydrate.

Expressed differently, the compound according to the inventioncorresponds to the following average formula:

[CH₃—CO—CH₂—CO—CH₃]₂Zn; x.H₂O;

in which x is a number which is an integer or otherwise, greater than orequal to 0.65.

More particularly, the zinc acetylacetonate used in the invention issuch that the abovementioned coefficient x is between 0.65 and 1.3.According to a more specific embodiment, the coefficient x is between0.7 and 1.2.

Preferably, a compound which is predominantly crystallized in the formof a .monohydrate compound is used. In other words, the coefficient x isof the order of 1.

The crystals of zinc acetylacetonate hydrate according to the inventionexhibit a limited acicular character (morphology different from that ofa needle).

It should be noted that this product may exist in the form of a powderbut also in a granulated or compacted form if necessary, subject to anappropriate forming step.

The zinc acetylacetonate may be obtained using conventional processeswith or without solvent.

Reference may be made, for example, to the manual “Metal β-diketonatesand allied derivatives” by R. C. Mehrota, R. Gaur, D. P. Gaur, whichappeared in 1978, Academic Press, in which various methods forsynthesizing these products are described.

A second subject of the present invention consists in another processwhich makes it possible to obtain zinc acetylacetonate hydrate.

This process consists in bringing a zinc oxide and/or hydroxide andacetylacetone into contact, in the presence of a solvent; the solventbeing used in a quantity of between 20 and 200 parts by weight, per 100parts by weight of acetylacetone.

Preferably, the content of solvent is less than or equal to 100 parts byweight relative to the same reference.

According to a more specific variant of the invention, the quantity ofsolvent used is at least 40 parts by weight relative to the samereference, and preferably at least 50 parts by weight.

Thus, one embodiment of the process according to the invention consistsin using a quantity of solvent of between 20 and 100 parts by weight per100 parts by weight of acetylacetone, more particularly between 40 and100 parts by weight, and preferably between 50 and 100 parts by weight.

The solvent used in the reaction is more particularly a compound capableof solubilizing acetylacetone and it is preferably inert towards theconstituents of the reaction mixture, under the reaction conditions.

According to a particularly advantageous variant of the presentinvention, the solvent is chosen from compounds whose boiling point isat most 100° C., measured at atmospheric pressure.

Among the compounds which can be used as solvents, there may bementioned, with no limitation being intended, C₁-C₆ aliphatic alcoholssuch as methanol, ethanol or propanol. Also suitable are ketones, suchas acetone; compounds comprising amide functions, such as formamide ordimethylformamide; compounds which are aromatic, such as benzene, oroptionally comprising one or more alkyl substituents.

Obviously, using a combination of the solvents indicated above will notdepart from the scope of the present invention.

The bringing into contact takes place, in addition, in the presence ofan acetylacetone/zinc oxide and/or hydroxide molar ratio of between 2/1and 2.4/1. Preferably, the process according to the invention is carriedout in the presence of a molar ratio of between 2/1 and 2.2/1. Accordingto a particularly advantageous variant of the present invention, thebringing into contact takes place with an acetylacetone/zinc oxideand/or hydroxide molar ratio close to the stoichiometric value.

The bringing into contact takes place with stirring.

Preferably, the reaction is carried out in a turbosphere-type reactor,or any other apparatus provided with mechanical stirring means allowinggood homogenization of a heterogeneous reaction mixture.

According to a specific embodiment of the invention, the bringing intocontact is carried out by introducing the acetylacetone into a zincoxide and/or hydroxide and solvent mixture.

The bringing into contact of the reagents is carried out while thetemperature is preferably maintained between room temperature and about100° C. More particularly, the bringing into contact takes place at atemperature of less than 80° C. According to a preferred variant of theinvention, the bringing of the acetylacetone into contact with the oxideand/or hydroxide is carried out at a temperature of less than or equalto the reflux temperature of the solvent used (or the solvent mixture).

The bringing into contact may be carried out under an inert atmosphere(such as nitrogen or a rare gas) or under air.

The duration of the operation is conventionally one hour to 4 hours.

Once the introduction has been carried out, the stirring and thetemperature are preferably maintained for one to two hours.

After this preferred finishing step, the solvent is removed from thereaction mixture.

The procedure is preferably carried out by distillation.

An advantageous embodiment of the invention consists in carrying out theremoval of the solvent in two successive steps. Thus, the first steptakes place under atmospheric pressure, by uniformly increasing thetemperature so as to distil the solvent without removing the waterpresent. The second step takes place under reduced pressure so as toremove the remaining traces of solvent.

During this second step, the procedure is carried out such that thecontent of water in the zinc acetylacetonate hydrate obtained remains inthe range indicated above.

It should be noted that the process according to the invention makes itpossible to limit the acicular character of the crystals obtained, thatis to say not to promote the growth of the crystals in the form of aneedle. Without wishing to be limited by any theory, it has beenobserved that crystals exhibiting a pronounced acicular character had agreater ability to cake, or to flow less well.

At the end of the process according to the invention, a product isobtained in the form of a finely divided powder, which it can beenvisaged to form, in particular by means of a granulation or compactionstep.

The importance of the process according to the invention is that itmakes it possible to cumulate, very advantageously, the advantages ofthe conventional processes without solvent and with solvent, withouthaving the disadvantages thereof.

Indeed, the processes using solvents have the advantage of exerting agood control of the exothermicity of the reaction, but in return, theyare not very productive. On the other hand, the processes withoutsolvent are very productive but can cause difficulties for appropriatelycontrolling the heat released during the reaction.

However, unpredictably, the process according to the invention is notonly a productive process, but it also makes it possible to correctlycontrol the heat of reaction.

As was indicated above, the zinc acetylacetonate monohydrate which hasjust been described is used as stabilizing agent for halogenatedpolymers, which are more particularly chlorinated polymers.

The zinc acetylacetonate monohydrate has an effect on the thermalstability of the polymer, but also on its stability towards light.

According to a specific characteristic of the invention, the content ofzinc acetylacetonate monohydrate is more precisely between 0.01 and 2 gper 100 g of halogenated polymer. More particularly, the content of thiscompound is between 0.05 and 1 g in relation to the same reference.

The invention is particularly well suited to the stabilization offormulations based on poly(vinyl chloride) (PVC).

Poly(vinyl chloride) is understood to mean compositions whose polymer isa homopolymer of vinyl chloride. The homopolymer may be chemicallymodified, for example by chlorination.

Many copolymers of vinyl chloride can also be stabilized using thecomposition according to the invention. These are in particular polymersobtained by copolymerization of vinyl chloride with monomers having anethylenically polymerizable bond, such as for example vinyl acetate,vinylidene chloride; maleic acid, fumaric acid or esters thereof;olefins such as ethylene, propylene, hexene; acrylic or methacrylicesters; styrene; vinyl ethers such as vinyl dodecyl ether.

Usually, the copolymers contain at least 50% by weight of vinyl chlorideunits and preferably at least 80% by weight of such units.

PVC alone or in a mixture with other polymers is the chlorinated polymermost widely used in the stabilized formulations according to theinvention.

In general, any type of poly(vinyl chloride) is suitable, regardless ofits mode of preparation. Thus, the polymers obtained, for example, usingprocesses intermass, in suspension or in emulsion may be stabilizedusing the composition according to the invention, regardless of theintrinsic viscosity of the polymer.

The formulations may contain the stabilizing additives conventionallyused in the field.

Thus, there may be mentioned the hydrochloric acid scavenging compoundswhich may be of the organic type or of the inorganic type, and may bepresent alone or in the form of mixtures

Among the hydrochloric acid scavengers of the organic type, there may bementioned more particularly the compounds comprising an alkaline-earthmetal or a metal chosen from columns IIB, IIA and IVB of the periodictable of elements (which appeared in the supplement to Bulletin de laSociété Chimique de France, no. 1, January 1966).

The cations are more particularly preferably chosen from calcium,barium, magnesium, strontium, zinc, cadmium, tin or lead.

It should be noted that it is possible to envisage combinations such as,for example, a mixture of hydrochloric acid scavenger based on calciumand zinc, barium and zinc, barium and cadmium, the first combinationbeing preferred.

As regards the hydrochloric acid scavenger compounds of the organic typecomprising at least one of the elements of columns IIB and IIA, theremay be mentioned most particularly the salts of organic acids, such asaliphatic or aromatic carboxylic acids, or fatty acids, or aromaticalcoholates or phenolates.

The ones most commonly used are, for example, the salts of the IIA orIIB elements of maleic, acetic, diacetic, propionic, hexanoic,2-ethylhexanoic, decanoic, undecanoic, lauric, myristic, palmitic,stearic, oleic, ricinoleic, behenic (docosanoic), hydroxystearic,hydroxyundecarioic, benzoic, phenylacetic, para-tert-butylbenzoic andsalicylic acids, phenolates, alcoholates derived from naphthol orphenols substituted with one or more alkyl radicals, such asnonylphenols.

For practical reasons or for economic reasons there are preferablychosen among the abovementioned alkaline-earth metal organic compounds,alkaline-earth metal propionate, alkaline-earth metal oleate,alkaline-earth metal stearate, alkaline-earth metal laurate,alkaline-earth metal ricinolate, alkaline-earth metal docosanoate,alkaline-earth metal benzoate, alkaline-earth metalpara-tert-butylbenzoate, alkaline-earth metal salicylate, alkaline-earthmetal and mono(2-ethylhexyl) maleate, alkaline-earth metalnonylphenates, alkaline-earth metal naphthenate and among theabovementioned organic compounds of cadmium, cadmium propionate, cadmium2-ethylhexanoate, cadmium laurate, cadmium stearate, cadmium salicylate,cadmium and mono(2-ethylhexyl) maleate, cadmium nonlyphenates andcadmium naphthenate.

As regards the organic-type compounds comprising lead, there may bementioned in particular those described in ENCYCLOPEDIA of PVC byLeonard I. NASS (1976), page 299-303.

They are very diverse compounds of which the most commonly used aredibasic lead carbonate, tribasic lead sulphate, tetrabasic leadsulphate, dibasic lead phosphite, lead ortho-silicate, basic leadsilicate, coprecipitate of lead silicate and sulphate, basic leadchlorosili.cate, coprecipitate of silica gel and of lead ortho-silicate,dibasic lead phthalate, neutral lead stearate, dibasic lead stearate,tetrabasic lead fumarate, dibasic lead maleate, lead 2-ethylhexanoate,lead laurate.

As regards the compounds based on tin, reference may be made inparticular to the manual “PLASTICS ADDITIVES HANDBOOK” by GACHTER/MULLER(1985) pages 204-210 or in ENCYCLOPEDIA OF PVC by Leonard I. NASS (1976)pages 313-325.

They are more particularly mono- or di-alkyltin carboxylates and mono-or di-alkyltin mercaptides.

Among these compounds, those most commonly used are the derivatives ofdi-n-methyltin, di-n-butyltin or di-n-octyltin such as, for example,dibutyltin dilaurate, dibutyltin maleate, dibutyltin laurate-maleate,dibutyltin bis(mono-C₄-C₈-alkyl maleate), dibutyltinbis(lauryl-mercaptide), dibutyltin S-S′-(diisooctyl mercaptoacetate),dibutyltin β-mercaptopropionate, polymeric di-n-octyltin maleate,di-n-octyltin bis-S- S′ (isooctyl mercaptoacetate), di-n-octyltinβ-mercaptopropionate. The monoalkylated derivatives of theabovementioned compounds are also suitable.

As hydrochloric acid scavenger of the inorganic type, there may also bementioned aluminium and/or magnesium sulphates and/or carbonates, inparticular of the hydrotalcite type. It is recalled that the compoundsof the hydrotalcite type correspond to the following formula:Mg_(1−x)Al_(x) (OH)₂A^(n−) _(x/n).mH₂O, in which x is between 0 excludedand 0.5 A^(n−) represents an anion such as carbonate in particular, nvaries from 1 to 3 and m is positive.

It is also possible to use essentially amorphous compounds of formula(MgO)_(y), Al₂O₃, (CO₂)_(x), (H₂O)₂, in which x, y and z obey thefollowing inequalities: 0<x≦0.7; 0<y≦1.7 and z≧3. These compounds are inparticular described in Patent Application EP 509 864. Moreover, thecompounds called catoites of formula Ca₃Al₂(OH)₁₂ or Ca₃Al₂(SiO)₄(OH)₁₂are suitable as hydrochloric acid scavenging compounds of the inorganictype.

All the hydrochloric acid scavengers of the inorganic type cited aboveare suitable for carrying out the invention.

The content of scavenger of the inorganic type mentioned above is moreparticularly between 0.1 and 10 g per 100 g of halogenated polymer.Preferably, this content is between 0.3 and 3 g in relation to the samereference. According to a still more specific embodiment of theinvention, this content is between 0.3 and 1 g relative to 100 g ofhalogenated polymer.

The content of scavenger of the organic type is more particularlybetween 0.1 and 10 g per 100 g of halogenated polymer, preferablybetween 0.1 and 3 g relative to the same reference.

According to a first variant, there is used, in addition to the zincacetylacetonate monohydrate, at least one hydrochloric acid scavenger,comprising at least one scavenger of the inorganic type and at least onescavenger of the organic type chosen from the calcium and/or zinc saltsof carboxylic acids.

All the hydrochloric acid scavengers of the inorganic type cited aboveare suitable for carrying out the invention.

However, preferably, the scavenger of the inorganic type is chosen fromthe compounds of the following formula: Mg_(1−x)Al_(x) (OH)₂A^(n−)_(x/n).mH₂O, in which x is between 0 excluded and 0.5, A^(n−) representsan anion such as carbonate in particular, n varies from 1 to 3 and m ispositive.

As regards the scavenger of the organic type, the composition accordingto this first variant comprises at least one scavenger based on calcium,optionally combined with a scavenger based on zinc.

The salts of aromatic or aliphatic carboxylic acids or the fatty acidsindicated above are suitable for carrying out this first variant.

According to this first variant, the content of scavenger of theinorganic type mentioned above is more particularly between 0.1 and 10 gper 100 g of halogenated polymer. Preferably, this content is between0.3 and 3 g in relation to the same reference. According to a still morespecific embodiment of the invention, this content is between 0.3 and 1g relative to 100 g of halogenated polymer.

The content of scavenger of the organic type defined for this firstvariant is more particularly between 0.1 and 4 g per 100 g ofhalogenated polymer, preferably between 0.3 and 2 g in relation to thesame reference.

A second variant consists of a composition comprising, in addition tozinc acetylacetonate monohydrate, as hydrochloric acid scavenger, atleast one organic scavenger chosen from the compounds based on lead.

Lead salts are more particularly used among those described above.However, according to a preferred embodiment, the lead salts used arechosen from lead phosphite combined with neutral or dibasic leadstearates, tri- or tetrabasic lead sulphates optionally combined with atleast one neutral or dibasic lead stearate.

According to this second variant, the composition comprises a content ofscavenger of the organic type based on lead of between 1 and 10 g per100 g of halogenated polymer.

In accordance with a specific embodiment of this second variant, thecomposition comprises, in addition, at least one scavenger of theorganic type chosen from the calcium salts of carboxylic acids describedabove.

According to a specific embodiment, the content of scavenger of theorganic type mentioned above is betwseen 0.1 and 3 g per 100 g ofhalogenated polymer.

A third variant consists of a composition comprising, in addition tozinc acetylacetonate monohydrate, at least one organic scavenger chosenfrom tin salts.

All the tin-based compounds described above may be chosen as constituentelements of the composition according to this third variant.

More particularly, the stabilizing composition has a content ofscavenger of the organic type mentioned above of between 0.1 and 3 g per100 g of halogenated polymer, preferably of between 0.2 and 2 g inrelation to the same reference. According to a more specific embodimentof this variant, the content of scavenger based on tin is between 0.3and 1 g per 100 g of halogenated polymer.

The formulations according to the invention may also comprise, ifnecessary, at least one free β-diketone.

More particularly, the β-diketones are chosen from compoundscorresponding to the formula (I) R¹COCHR²COR³, in which formula, R² andR³, which are identical or different, represents a C₁-C₃₀ hydrocarbonradical and R² represents a hydrogen atom or a C₁-C₄ alkyl radical.

More particularly, the R¹ or R³ radicals of the said β-diketone, whichare identical or different, represent a linear or branched, C₁-C₂₄ alkylor alkenyl radical; a C₆-C₃₀ aryl radical, substituted or otherwise withat least one alkyl radical and/or a halogen atom and/or a silicon atom;a C₃-C₁₄ cycloaliphatic radical and optionally capable of containingcarbon-carbon double bonds.

More particularly, the R¹ and R³ radicals represent a linear or branchedC₁-C₁₈ alkyl radical; a C₆-C₁₀ aryl radical, substituted or otherwisewith at least one alkyl radical and/or one halogen atom; or acycloaliphatic radical as defined above.

The abovementioned radicals may be optionally modified by the presence,in the aliphatic chain, of one or more groups of formula —O—, —CO—O—,—CO—. Preferably, the radicals do not comprise such functions.

According to another variant, the R¹ and R³ radicals may be linked toeach other such that the β-diketone forms a ring.

The R² radical may be either a hydrogen atom, or a C₁-C₄ alkyl radicalwhose aliphatic chain may be interrupted by one or more groups offormula —O—, —CO—O—, —CO—.

Preferably, R² represents a hydrogen atom or a methyl radical.

By way of example of such compounds, there may be mentioned mostparticularly octanoylbenzoyl-methane, stearoylbenzoylmethane,dibenzoylmethane or acetylbenzoylmethane.

The content of free β-diketone is usually between 0.05 and 1 g per 100 gof halogenated polymer.

It should be noted that the formulation may even comprise a β-diketonein the form of a calcium, magnesium or zinc chelate (with the exceptionof zinc acetylacetonate).

In this case, the content of this compound is between 0.05 and 1 g per100 g of halogenated polymer.

The formulation may, in addition, comprise at least one polyolcomprising 2 to 32 carbon atoms and having two to nine hydroxyl groups.

Among these compounds, there may be mentioned C₃-C₃₀ diols such aspropylene glycol, butanediol, hexanediol, dodecanediol, neopentylglycol, polyols such as trimethylolpropane, pentaerythritol,dipentaerythritol, tripentaerythritol, xylitol, mannitol, sorbitol,glycerin, mixtures of oligomers of glycerin having a degree ofpolymerization of 2 to 10.

Another family of polyols which may be suitably used consists of thepartially acetylated polyvinyl alcohols.

It is likewise possible to use hydroxylated compounds comprisingisocyanurate groups, alone or in combination with the abovementionedpolyols, such as for example tris(2-hydroxyethyl.)isocyanurate.

The quanity of polyol used is generally between 0.05 and 5 g per 100 gof halogenated polymer. More particularly, it is less than 2 g per 100 gof halogenated polymer.

It is possible, where appropriate, to incorporate into the compositionaccording to the invention compounds of the type including organicphosphites, such as for example trialkyl, aryl, triaryl, dialkylaryl ordiarylalkyl phosphites, for which the term alkyl designates hydrocarbongroups of C₈-C₂₂ polyols or monoalcohols, and the term aryl designatesaromatic groups of phenol or of phenol substituted with C₆-C₁₂ alkylgroups. It is likewise possible to use calcium phosphites, such as forexample compounds of the Ca(HPO₃).(H₂O) type as well asphosphite-hydroxy-aluminium-calcium complexes.

The content of additive of this type is usually between 0.1 and 2 g per100 g of halogenated polymer.

The stabilizing compositions according to the invention may likewisecomprise at least one synthetic, crystalline alkali metalaluminosilicate having a water content of between 13 and 25% by weight,having the composition 0.7-1M₂O.Al₂O₃.1.3-2.4SiO₂ in which M representsan alkali metal such as in particular sodium. Zeolites of the NaA type,as described in U.S. Pat. No. 4,590,233, are in particular suitable.

The content of this type of compound varies generally between 0.1 and 5g per 100 g of halogenated polymer.

The composition according to the invention may also comprise compoundsof the type including epoxides. These compounds are generally chosenfrom epoxidized polyglycerides, or epoxidized fatty acid esters, such asepoxidized linseed, soya bean or fish oils.

The quantity of compounds of this type usually varies between 0.5 and 10g per 100 g of halogenated polymer.

Other conventional additives in the field may be incorporated, ifnecessary, into the formulations stabilized according to the process ofthe invention.

Thus, the formulation may comprise white or coloured pigments.

By way of example of coloured pigments, there may be mentionedrare-earth-based compounds such as in particular cerium sulphide.

According to a specific variant of the invention, the compositioncomprises a white pigment which is most often titanium dioxide.

More particularly, the titanium dioxide is chosen in rutile form. Thesize of the titanium dioxide particles is generally between 0.1 and 0.5μm.

According to a specific embodiment of the invention, titanium dioxide isused in the form of rutile having been subjected to a surface treatment,preferably mineral.

Among the suitable titanium dioxides, there may be mentioned with nolimitation being intended, the titanium dioxide Rhoditan RL18 marketedby Millenium, the titanium dioxides Kronos 2081 and 2220 marketed byKronos.

The quantity of pigment introduced into the formulation comprising thepolymer varies within wide limits and depends on the colouring power ofthe pigment and on the desired final colour. However, by way of example,the quantity of pigment may vary from 0.5 to 15 g per 100 g ofchlorinated polymer.

In the particular case of titanium dioxide, the content may be moreparticularly between 0.1 and 20 g per 100 g of halogenated polymer,preferably between 2 and 15 g in relation to the same reference.

Other conventional additives may supplement the formulation, dependingon the application for which it is intended.

As a general rule, the formulation may comprise phenolic antioxidants,anti-UV agents such as 2-hydroxybenzophenones, 2-hydroxybenzotriazolesor sterically hindered amines, usually known by the term Hals.

The content of this type of additive generally varies between 0.05 and 3g per 100 g of resin.

If necessary, it is possible to use lubricants which will facilitate theprocedure, chosen in particular from glycerol monostearates or propyleneglycol, fatty acids or esters thereof, montanate waxes, polyethylenewaxes or oxidized derivatives thereof, paraffins, metal soaps,functionalized polymethylsiloxane oils such as for exampleγ-hydroxypropylenated oils.

The quantity of lubricant entering into the halogenated polymer-basedformulation varies in general between 0.05 and 2 g per 100 g of resin.

The formulation may also comprise plasticizers chosen from alkylphthalates. The compounds most generally used are chosen from di(2ethylhexyl) phthalate, esters of linear C₆-C₁₂ diacids, trimellitates orphosphate esters.

The quantity of plasticizing agent used in the formulations varies in abroad range depending on the rigid or flexible character of the finalpolymer. As a guide, the content varies from 5 to 100 g per 100 g ofhalogenated polymer.

The preparation of the formulations may be carried out by any meansknown to persons skilled in the art.

The conventional methods of incorporation are perfectly suitable forproducing the formulation based on PVC.

Thus, it is possible to carry out this operation in a mixer providedwith a paddle and counter-paddle system operating at a high speed.

Generally, a temperature at which the constituents of the formulationare incorporated is less than 130° C.

Once the mixture has been prepared, the composition is formed accordingto the usual methods in the field such as injection, extrusion-blowing,extrusion, calendering or moulding by rotation.

The temperature at which the forming is carried out varies in generalfrom 150 to 220° C.

Concrete but nonlimiting examples will now be presented.

EXAMPLE 1

224.2 g of zinc oxide and 300 g of solvent (acetonitrile/methanolmixture) are introduced into a turbosphere reactor. The mixture isheated to reflux temperature and 600 g of acetylacetone are added over aperiod of 1 hour while the reaction mixture is maintained under reflux.The mixture is maintained under reflux for an additional 1 hour and thenthe solvent is distilled under atmospheric pressure. When the solvent nolonger distils, the mixture is placed under a vacuum of 200 torr for 10minutes.

802 g of zinc acetylacetonate are recovered (water content 5.5%)

EXAMPLE 2

The procedure is carried out as in Example 1 except for the fact thatthe solvent consists of 300 g of methanol. Furthermore, the refluxingtime following the introduction of the reagents is 2 hours.

793 g of zinc acetylacetonate are recovered (water content 5.1%)

EXAMPLE 3

The procedure is carried out as in Example 1 except for the fact thatthe solvent consists of 300 g of 90% ethanol (the remainder beingwater).

801 g of zinc acetylacetonate are recovered (water content 6.3%).

What is claimed is:
 1. A method for stabilizing a halogenated polymercomprising incorporating in said halogenated polymer a stabilizingeffective amount of zinc acetylacetonate hydrate, wherein said zincacetylacetonate hydrate comprises between 4.4% and 8.8% by weight ofwater.
 2. The method according to claim 1, wherein the zincacetylacetonate has the following average formula:[CH₃—CO—CH₂—CO—CH₃]₂Zn; x.H₂O; in which x is a number which is aninteger or otherwise, greater than or equal to 0.65.
 3. The methodaccording to claim 2, wherein the coefficient x is between 0.65 and 1.3.4. The method according to claim 3, wherein the coefficient x is between0.7 and 1.2.
 5. A process for the preparation of zinc acetylacetonatehydrate, wherein said zinc acetylacetonate hydrate comprises between4.4% and 8.8% by weight of water, comprising contacting and reacting azinc oxide and/or hydroxide with acetylacetonate, in the presence of asolvent, wherein the quantity of solvent is between 20 and 200 parts byweight, per 100 parts by weight of acetylacetonate.
 6. The processaccording to claim 5 wherein the solvent is removed at the end of thereaction.
 7. The process according to claim 5, wherein the solventcomprises compounds which are inert under the reaction conditions andwhose boiling temperature is at most 100° C., measured at atmosphericpressure.
 8. The process according to claim 5, wherein the contacting iscarried out by introducing the acetylacetone into a zinc oxide and/orhydroxide and solvent mixture.
 9. The process according to claim 8,wherein the contacting is carried out at a temperature of less than orequal to the reflux temperature of the solvent.
 10. The processaccording to claim 5, wherein the quantity of solvent is between 20 and100 parts by weight per 100 parts by weight of acetylacetone.
 11. Theprocess according to claim 10, wherein the quantity of solvent isbetween 40 and 100 parts by weight per 100 parts by weight ofacetylacetone.